This invention relates in general to motion transmission and particularly to a system for converting rectilinear motion to continuous rotary motion for actuating a truck trailer landing gear apparatus.
It has long been known to equip truck trailers with so-called landing gear mechanisms having a pair of landing gear legs adapted to be extended by rotation of a transverse shaft or so-called cross shaft having a crank at one end. Thus, the landing gear legs can be lowered or extended by manually rotating the crank to lift the front of the trailer, as for disconnection from a truck tractor. The weight of a fully loaded trailer on the landing gear legs typically may exceed 30,000 lbs. Turning the crank by hand may require as much as about 100 lbs. of manual force on the crank handle to lift the heavily laden trailer. Moreover, it may typically take 25 turns by hand at these great forces to lift the trailer only one inch. Accordingly, this is a difficult and energy-consuming manual chore. Adverse weather conditions make the hard job of cranking even more difficult. The very high gear ratio necessitated by the landing gear mechanism to enable manually applied cranking force to lift such a great weight means that many difficult, time-consuming turns of the crank are necessary for either extending or retracting the landing gear legs. Damage to truck trailers which often results from not properly positioning the landing gear by manual operation often requires costly repairs which represent a major expenditure for truck owners. This occurs because of the frequent failure, due to high force and time required, to crank the landing gear legs completely down. Thus, when the tractor is pulled away from the trailer after having been unhitched, the front of the trailer will drop. The shock of the impact can damage the landing gear and the frame of the trailer. Later, when a tractor is backed under the trailer for hitching purposes, damage can again be done to the leading edge of the trailer and also to the tractor drive train, as well as possibly causing the trailer to be rammed or jammed against a loading dock with consequent damage to the dock, the rear of the trailer, or both.
There is disclosed in U.S. Pat. No. 4,116,315 a pneumatic landing gear actuator for making advantageous use of air pressure normally provided on truck trailers for braking purposes in order to rotate shaft extensions to each landing gear leg. Such apparatus makes use of a pneumatic actuator of the type previously known for applying actuating vehicular brakes having very limited piston rod travel. Therefore, only a most limited arcuate movement is available for each actuating stroke of the device. Additionally, such landing gear actuator imparts rotation to the landing gear shafts only upon one direction of movement of a piston rod of the pneumatic actuator, thus even more limiting the speed and effectiveness of the patented device. When such device is utilized for actuating the landing gear mechanism when the legs are not in a loaded condition, i.e., for lowering the landing gear legs several inches to the ground or raising them, the limited actuating stroke and single-acting character of the patented device result in very long actuating times with consequent high usage of air in an inefficient manner.
It is an object of the present invention to provide a motion converting system whereby reciprocal rectilinear motion may be converted to continuous rotary motion in an economic and highly efficient manner.
It is another object of the present invention to provide a motion converting system of the type stated wherein despite the direction of rectilinear travel continuous rotary motion is developed.
It is a further object of the present invention to provide a system of the character stated which requires a paucity of parts, all of which are of sturdy construction and thus resistant to breakdown and productive of reliable operation whereby said system may be most economically manufactured and which is exceedingly durable in operation, not requiring the costly services of an attendant.
It is a still further object of the present invention to provide a motion converting system of the character stated wherein the means for imparting reciprocal rectilinear motion to a rod or like member may be of any suitable type whether pneumatic, hydraulic, electro-mechanical, or the like so that extreme versatility in production is feasible.
It is another object of the present invention to provide a motion converting system of the character stated incorporating a novel linkage system between the rectilinearly moving system and a driven shaft for effecting operation of an unusual and novel double ratchet arrangement for cooperation with a toothed wheel alternatively drivenly engageable with said ratchets responsive to the direction of travel of the rectilinearly movable members.
It is a further object of the present invention to provide a motion converting system of the type stated for operating a vehicular jacking mechanism having a shaft which is rotatable for actuating a jacking member.
It is a still further object of the present invention to provide such a motion converting system for operating a truck trailer landing gear mechanism.
It is another object of the present invention to provide such a motion converting system for operating a truck trailer landing gear mechanism with high efficiency, with speed, and in a manner which is easily controlled, with motive power being provided by the conventional vehicular air source such as braking air pressure.
It is still another object of the present invention to provide such motion converting system which is easily installed upon a truck trailer for operating a conventional crank-type landing gear mechanism by causing rotation of a so-called cross shaft of the mechanism normally turned by hand cranking, a related object of the invention being to provide such a motion converting system which is fitted on such cross shaft with the shaft intact for suspending the system beneath a truck trailer.
A further object of the present invention is to provide such a motion converting system for operating a landing gear mechanism at a selected mechanical ratio for extra high speed movement of the landing gear legs under lightly loaded or unloaded conditions.
Among other objects of the present invention may be noted the provision of such a motion converting system for operating a landing gear mechanism which is relatively lightweight, which is installed very quickly and easily, which is low in cost, reliable in use, which develops high torque with low air consumption, which operates from minimum air pressure, and which provides sufficient actuating power to lift even a fully loaded trailer with high speed, and which permits manual operation of the landing gear mechanism.
Other objects will be in part apparent and in part pointed out hereinafter.